1. Evolution
Year 10 Life Science

2. Evolution Natural Selection
Evolution is the gradual development of different species from a common ancestor over time A species gradually becomes better Adapted to its environment
Natural Selection

3. similar structure and provide evidence of an evolutionary relationship
Homologous Structure
similar structure and provide evidence of an evolutionary relationship

4. Homologous Structure
Homologous structures are features of organisms that have a similar structure and provide evidence of an evolutionary relationship
Similar structure, closely related, different function
E.g. wing of bird, wing of bat, leg of lizard, flipper of whale, arm of human all have same basic structure
Pentadactyl limb (having 5 digits)
However, in each organism is has been modified to suit a different way of life.

5. Analogous Structures
These structures may have come about, due to the environment in which they live in.

6. Analogous Structures
Analogous characteristics are those that look similar but are genetically very different. (no evolutionary relationship)
Similar Structure. Not Related. Same environment
These structures may have come about, due to the environment in which they live in.
Eg. sharks and dolphins seem similar in appearance however genetically these animals are completely different.
Both need flippers, to be able to swim in the water.
A butterfly and a Bird are completely different species, but both have the similar structure of ‘wings’ to enable them to fly

7. Divergent evolution
Divergent evolution: formation of new species due to change in environment
When two or more species evolve from a common ancestor
Example: Finches on the Galapagos Islands
Evolved into different species to eat different foods

8. Convergent evolution
Where two organisms have similar analogous structures but different ancestors (not related)
When two or more unrelated species adopt similar adaptations in response to common environmental conditions
Example:  Sharks and dolphins are similar in appearance but are not related

9. Lamarck's Theory
According to Lamarck’s theory, organisms will evolve over time based on the repeated use of body structures.
Evolution by inheritance of acquired characteristics

10. In this example, the Ancestral form consumed plant material and needed extra height to reach the higher branches. Over time, the animal evolved because of constant use of neck muscles and leg muscles to reach higher branches.
Lamarck's Theory
Giraffe's inherited long necks from short necked ancestors
who continually stretched their necks to reach food

11. Darwin’s Theory
Long necked and short necked giraffes once existed together
but the long-necked giraffe had an adaptive advantage
Darwin proposed that variation was critical in understanding how species change over long periods of time. His argument was that selection can not occur without differences in a population (variation)

12. Explain how the evolution shown in the diagram below would have occurred according to Lamarck’s theory.

13. answer
The ancestral organism stretched its legs to reach the higher branches.
This ‘stretched leg’ characteristic (an acquired characteristic) was inherited by the offspring.
These offspring in turn stretched further and then passed on their ‘stretched leg’ characteristic to their offspring.
The long-legged form shown eventuated from this stretching and inheritance.

14. Speciation
The theory of evolution by natural selection proposes that all species are related.
Some species more closely related than others, but ultimately all life should be able to be traced back to one original species.
A change in species is usually due to some form of isolation from an original population

15. speciation Speciation is the process by which one species
splits into two or more separate species.
The process of speciation occurs in three steps:
Variation: There must be variation in the population
Isolation: This means that different groups must be prevented from interbreeding, this stops any differences from one population reaching the other population
Selection: Natural selection affects the genotype and causes changes (mutations) that prevent the groups breeding even if they got back together.

16. speciation

17. example

18. questions
1. Describe two ways in which a population may become geographically isolated to form two populations?
Ocean, river, mountains, earthquake, sand blocking an estuary, desert/dry conditions, gorge
2. Suggest two reasons why the two separated populations may evolve differently
Different mutations occur in each population. Differences in conditions would mean that different characteristics are ‘selected for’ in each population

19. questions
3. The group of flightless birds, known as ratites, occur in Australia (emu), New Zealand (kiwi), South America (rhea), Pupua New Guinea (cassowary) and Africa (ostrich). How can the distribution of these related species be explained?
The ancestral ratite lived on Gondwana (one land mass). When this split to form the continents, the ratites on each continent evolved in isolation, giving rise to the different forms/new species.

20. Artificial Selection vs Natural selection
Artificial selection is the process by which humans deliberately choose to breed particular organisms with desirable features.
Eg. domesticated dogs, different breeds of dogs are all one species and different breeds produced by Artificial selection.
Natural Selection is the process by which the environment acts on the population

21. Human Evolution
The name of our species “homo sapiens” means the “wise man.”
According to fossils we have been around for about 200,000 years.
Fossils indicate other human-like species have existed too.

22. Primates, Hominids and HominiNs
Primates include lemurs, monkeys, apes, gibbons and humans.
To be classified in this species the organism must have “grasping hands, nails rather than claws and forward facing eyes”
Hominids include apes, chimps and humans. (no tail)
Hominins are humans and their common ancestors. There are key differences which show how different Humans now are from their original primate ancestors.

23. How structures have changed….
Humans are now a ‘sub-tribe’ as they have the ability to walk on 2 legs (known as bipedalism)
Differences between primates and humans include:
Skull
Size
Jaw shortens
location of foramen magnum
Vertebral Column (S Shaped)
Pelvis (wider)
Femur (angled inwards)
Feet (flat)

28. Summary/keywords Pentadactyl limb  having 5 digits
Homologous structure  Features of
organisms that have a similar structure
and provide evidence of an evolutionary relationship (common ancestor).
Do not have to have the same function in all species.
Analogous structure  Similar Structure. Not Related. These structures may have come about, due to the environment in which they live in.
Divergent Evolution  When two or more species evolve from a common ancestor
Convergent Evolution  When two or more unrelated species adopt similar adaptations in response to common environmental conditions

29. Summary/keywords
Artificial selection humans deliberately choose which individuals will mate
Natural selection the environment acts on the population
Darwin’s theory selection cannot occur without differences in a population
Lamarck’s theory Evolution by inheritance of acquired traits
Genetic isolation keeping potentially interbreeding groups apart by some barrier
Evolution  the gradual development of different species from a common ancestor